1. Field of the Invention
The present invention is directed to a taphole mix for a molten metal discharge port which is used under a reducing atmosphere at a port for discharging a molten metal, for instance, in a blast furnace, an electric furnace and the like.
2. Prior Art
Certain materials have heretofore been known and employed as taphole mixes for use in a molten metal discharge port in which a principal base material composed of ROSEKI, chamotte and/or alumina is mixed and kneaded with a silicon carbide, a carbonaceous material, a Ferro-silicon nitride and the like and a clay, and further in which a coal tar having a fixed carbon content of not more than 31.5% is used as a binder. In regard to the coal tar noted here, a grade with a fixed carbon content of about 27 to 31% (100 to 400 cp viscosity at 60.degree. C. ), is commercially available but grades of 31.5% or more in fixed carbon content have not yet been obtained commercially and hence have not been used to date.
Nevertheless, in order to prolong the tapping time of molten iron, it is important that a taphole mix for use in a molten metal taphole should be resistant to both wear and corrosion from the molten iron and associated slag. However, the above conventional taphole mixes are not satisfactory with respect to these physical properties. Japanese Patent Laid-Open No. 1-108170, for example, discloses a taphole mix for use in a molten iron taphole in a blast furnace, characterized in that such taphole mix comprises an alumina material in an amount of 30 to 58 wt %, a magnesia-alumina spinel material in an amount of 10 to 30 wt % and a carbon material in an amount of 10 to 20 wt %, a ferrosilicon as a bonding agent in an amount of 3 to 10 wt %, a clay in an amount of 3 to 10 wt % and an anhydrous tar as a binder in an amount of 10 to 20 wt %. Although capable of exhibiting improved corrosion resistance, this known taphole mix does not have enough strength to attain excellent wear resistance.
Furthermore, Japanese Patent Publication No. 57-23675 discloses a taphole mix for a molten iron taphole in a blast furnace, characterized in that such taphole mix comprises an inorganic composition derived by mixing a coke in an amount of less than 40 wt %, a silicon carbide in an amount of 5 to 40 wt %, a ROSEKI in an amount of 10 to 50 wt % and a silicon alloy in an amount of 2 to 10 wt %, the silicon alloy having a silicon metal content of more than 75%, and then adding and mixing a phenolic resin solution in an organic solvent in an amount of 10 to 35 wt % to the composition. However, this known taphole mix does not have sufficient low-temperature strength, or satisfactory low-temperature wear resistance. A further problem with this taphole mix is that due to a rather large difference in strength at high- and low-temperatures, the mix is prone to crack during drilling so that drilling becomes difficult.
Accordingly, the object of the present invention is to provide a taphole mix for use in a molten metal taphole which exhibits improved wear resistance and corrosion resistance properties and that enables molten iron to prolong a tapping time and occurrence of difficult drilling to be minimized.